A novel metal-free organobase-catalyzed regioselective benzoylation of diols and carbohydrates has been developed. Treatment of diol and carbohydrate substrates with 1.1 equiv. of 1-benzoylimidazole and 0.2 equiv. of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in MeCN under mild conditions resulted in highly regioselective benzoylation for the primary hydroxyl group. Importantly, compared to most commonly
The first catalytic process for protection of hydroxyl groups in sugars has been developed. Highly regioselective protection was accomplished along with high chemical yield. The regioselectivity of the benzoylation was realized as an intrinsic character of sugars based on a stereorelationship among their hydroxyl groups. Furthermore, complete protection of alpha-methyl glucoside and beta-methyl xyloside
Chelation-controlled regioselectivity in the lanthanum-promoted monobenzoylation of monosaccharides in water
作者:Ian James Gray、Ronald Kluger
DOI:10.1016/j.carres.2007.05.024
日期:2007.10
formation of the ester, which competes with hydrolysis of BzMP, to give an estimate of the efficiency of the conversion of the sugar. Higher conversions can be achieved using excess reagent. Regioselectivity is influenced by the structure of the glycoside. For example, the reaction leads to different product distributions from alpha- and beta-anomers of the glycosides. The reaction combination provides a
containing cis-vicinal diol, the substrate scope also includes glycosides without cis-vicinal diol. For such a substrate scope, usually, only methods using stoichiometric amounts of organotinreagents can lead to the same protection pattern with high selectivities and highly isolated yields (84–97% in most cases). Therefore, SnCl2, as a low toxicity and extremely cheap reagent, should be the best catalyst
Lead-Catalyzed Aqueous Benzoylation of Carbohydrates with an Acyl Phosphate Ester
作者:Yuyang Li、Ronald Kluger
DOI:10.1021/acs.joc.7b03142
日期:2018.7.20
with benzoyl methyl phosphate (BMP) and triethylamine in water with added lead nitrate produces monobenzoyl esters in up to 75% yield. This provides a water-compatible pathway for novel patterns of benzoylation of polyhydroxylic compounds.